Hairs

1
Chapter 8

• Hairs fibers

2
Hair anatomy
3
Hair forensics

• Hair shaft
• Cuticle
• Cortex
• Medulla

4
Hair cuticles

• Scale patterns vary by species

Human Cat Otter
5
Hair cortex

• Pigment granules
• Color, shape distribution

Eumelanin is the dark pigment which predominates
in black and brunette hair. Phaeomelanin is a
lighter pigment, which is found in red and blond
hair
6
Hair cortex
7
Hair medulla

• Vary by species
• Medullary index (diameter of medulla/ diameter of
  hair shaft)
• Humans lt0.33
• Animals gt0.5

8
Hair medulla

• Medulla patterns vary by individual hairs and by
  species

(fragmented) (interrupted)
9
Hair root growth phases

• Phase of growth
• Anagen follicle actively producing hair
• Telogen Growth ends, hair shed in 2-6 mos.

10
Hair root
11
Distinguishing human hairs

• Racial origins

12
Distinguishing human hairs

• Body location

Limb fragmented/trace medulla
Beard double medulla
Pubic continuous medulla
13
Distinguishing human hairs

• Body location

14
Misc. hair characteristics

• Lice egg sac Dyed

15
Hair microscopy

• There are three basic conclusions that can be
  reached from a microscopic examination and
  comparison of hairs
• The hairs from the questioned (Q) source exhibit
  the same microscopic characteristics as the hairs
  in a known (K) hair sample and can be associated
  to the source of the known hairs.
• The hairs from the questioned source are
  microscopically dissimilar to the hairs in a
  known hair sample and cannot be associated with
  the source of the known hairs.
• The questioned hairs exhibit both similarities
  and slight differences to hairs found in a known
  hair sample, and no conclusion can be reached
  whether they could have originated from the known
  source. It may be that, in the opinion of the
  examiner, the differences are not sufficient to
  eliminate the source of the known hairs as being
  a possible source of the questioned hairs. At the
  same time, the presence of these differences
  precludes an association being made between the
  questioned and known hairs.

16
Online Hair resources

• Microscopy of Hair Part 1 A Practical Guide and
  Manual for Human Hairs
• http//www.fbi.gov/hq/lab/fsc/backissu/jan2004/res
  earch/2004_01_research01b.htm